A distinction is made in the art between so-called closed or endless clamp structures made from tubular stock and so-called open clamp structures made from band material. In contrast to the former, the latter have to have their open ends, which usually overlap, mechanically connected in use. In addition to these clamp structures, devices for fastening, for example, cable strands are known in the prior art which are made from plastic material with serrations at one end adapted to engage in an eyelet with or without detent at the other end. Clamp structures, to be successful these days, especially in applications utilizing relatively hard and thin plastic hoses, such as in the automotive industry, must be able to assure internal clamping surfaces devoid of any discontinuity, steps or offsets to assure a fluid-tight connection. Moreover, there is an ever-present desire to simplify the construction and therewith reduce the manufacturing cost of clamp structures meeting these requirements.
Clamp structures are known in which hook-like elements are provided near one end which are adapted to engage in an eyelet at the other end. For example, Swiss Patent 153,565 discloses a clamp structure consisting of a clamping band provided with outwardly extending detent members at one end adapted to engage with the edge of a transverse slot provided in an enlarged part of the opposite end. Apart from wastefulness in the loss of material as a result of the enlarged end part, the clamp structure disclosed in this patent does not satisfy the requirements for fluid-tight connection.
The German Offenlegungsschrift 23 59 284 discloses a clamp structure which includes a tongue-like extension near one end provided with outwardly extending teeth while the opposite end is provided with a slot-like opening into which the tongue-like extension is able to extend so that a springy tongue spaced from the opposite end which projects into the slot-like opening is able to engage with the teeth on the tongue-like extension during tightening of the clamp structure. Apart from a limited holding ability of the clamp structure disclosed in this patent, they also do not assure a completely fluid-tight installation because of the existence of internal steps, offsets or discontinuities.